JPH10333067A - Multibeam scanning optical system and coupling optical system therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new multibeam scanning optical system capable of performing excellent multibeam scanning by effectively joining two or more light beams without using an expensive optical element such as a polarizing beam splitter. SOLUTION: Coupling lenses 2, 2' provided for every light source are arranged in the direction corresponding to main scanning by making their optical axes parallel to each other and compose a coupling lens group, a beam combiner 4 having a negative power at least in the direction corresponding to main scanning is used in common for the respective light beams between the coupling lens group and the deflection/reflection surface 6 of a light deflector and the positional relations of the respective light sources 1, 1' to the optical axes of the corresponding coupling lenses 2, 2' are adjusted so that the coupled light beam by the corresponding coupling lenses 2, 2' is made incident on the combiner 4 in the direction corresponding to main scanning while mutually narrowing their interval and made incident on the combiner 4 in the direction corresponding to sub-scanning while mutually widening their interval.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multi-beam scanning optical system and a coupling optical system for the multi-beam scanning optical system.

[0002]

2. Description of the Related Art Light beams from a plurality of light sources are deflected by a common light deflector, and each deflected light beam is condensed as a light spot on a surface to be scanned by a common scanning and image forming optical system. Various "multi-beam scanning optical systems" for scanning a line have been proposed.

As a method of combining light beams from a plurality of light sources, a method using a polarizing beam splitter is known. However, only one polarizing beam splitter can combine light beams.
Limited to light beams, two or more polarizing beam splitters are required to combine three or more beams, or two light beams to be combined need to be orthogonally incident on the polarizing beam splitter. There is a problem that the space is large, and further, the cost of the scanning optical system is high because the polarizing beam splitter is expensive.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a novel multi-beam capable of effectively combining two or more light beams and performing good multi-beam scanning without using an expensive optical element such as a polarizing beam splitter. It is an object to realize a scanning optical system.

Another object of the present invention is to realize a coupling optical system for a multi-beam scanning optical system suitable for the multi-beam scanning optical system.

[0006]

According to a first aspect of the present invention, there is provided a multi-beam scanning optical system, wherein light beams from a plurality of light sources are individually coupled by a coupling lens provided for each light source, and each light beam is shared. Are focused in the sub-scanning corresponding direction by the cylinder lens, and formed as a long line image in the main scanning corresponding direction in the vicinity of the deflecting reflection surface of the common optical deflector, and each deflected light beam deflected by the optical deflector is shared. A multi-beam scanning optical system that converges as a light spot on a surface to be scanned by a scanning imaging optical system and scans a plurality of scanning lines at once, and includes a coupling lens group and a beam combiner.

In this specification, the "main-scanning corresponding direction / sub-scanning corresponding direction" is a direction parallel to the main and sub-scanning directions on the optical path from the light source to the surface to be scanned.

[0008] The "coupling lens group" is configured by arranging coupling lenses provided for each light source in the main scanning corresponding direction with their optical axes parallel to each other. The “beam combiner” is a “optical element common to each light beam” that is provided between the coupling lens group and the deflecting / reflecting surface of the optical deflector.
Has a negative power at least in the main scanning corresponding direction. In the `` each light source '', the light beams coupled by the corresponding coupling lenses enter the beam combiner while narrowing the interval in the main scanning corresponding direction, and increase the beam interval in the sub-scanning corresponding direction. The positional relationship with the optical axis of the corresponding coupling lens is adjusted so that the light enters the combiner or the cylinder lens.

The lens action of each coupling lens constituting the coupling lens group may be a “collimating action” for converting a light beam from a corresponding light source (a semiconductor laser or an LED can be suitably used) into a parallel light beam. Item 8), a light beam from the corresponding light source is referred to as a “light beam having a weak focusing property”.
Alternatively, it may be an action to make a “weakly divergent light beam”.

As the common "optical deflector", a well-known polygon mirror, rotating two-sided mirror, rotating single-sided mirror, or the like can be used.

In the multi-beam scanning optical system according to the first aspect of the present invention, it is preferable that the light beams passing through the beam combiner and the cylinder lens cross each other at a position near the deflecting reflection surface of the optical deflector in the main scanning corresponding direction. , Optical arrangement "(claim 2). In this way, after being deflected, each light beam is separated in the main scanning corresponding direction and passes through substantially the same optical path in the main scanning corresponding direction with a time difference from each other, so that each light beam has the same optical characteristics.

Further, in the multi-beam scanning optical system according to the first or second aspect, it is preferable that the scanning and imaging optical system common to each deflected light beam has an fθ lens and a long lens for correcting surface tilt, Each light beam that has passed through the beam combiner and the cylinder lens becomes f
The optical arrangement is determined so as to intersect between the θ lens and the long lens for correction (claim 3). In this case, the operation of the scanning image forming optical system is the same for each deflected light beam in the sub-scanning corresponding direction.
Other examples of the “scanning optical system” include a concave mirror having a function of making the main scanning uniform, a combination of a concave mirror and a long lens, or the like.

In the case where the lens action of the coupling lens in the coupling lens group is not a collimating action and the coupled light flux is a weak divergent or weakly converging light flux, "scanning is made uniform. A “lens having a function” is not strictly an fθ lens, but it is thought that there is no risk of confusion, so in this specification,
Even in the case described above, a lens having a function of making the scanning speed uniform is referred to as an fθ lens.

In the multi-beam scanning optical system according to the first, second, or third aspect, the "beam combiner" may use a mirror (spherical surface, cylinder surface, toroidal surface, etc.) having negative power. A single lens having power (a spherical lens, a cylinder lens, a toroidal lens, etc.) "can be suitably used (claim 4).

The beam combiner and the cylinder lens are both provided between the coupling lens group and the deflecting / reflecting surface. The order is such that the beam combiner is arranged closer to the coupling lens group side than the cylinder lens. Alternatively, the cylinder lens may be positioned closer to the coupling lens group than the beam combiner.

The beam combiner (Claim 4) and the cylinder lens configured as a single lens having negative power can be combined with each other and integrated (Claim 6). The number of light sources and coupling lenses may be three or more, but may be two (claim 7).

The "coupling optical system" according to claims 9 to 14 is an optical system used as a coupling lens group in the multi-beam scanning optical system according to any one of claims 1 to 7. , "Coupling lenses that are optically equivalent to each other are arranged and integrated in one line with their optical axes parallel to each other corresponding to each of the light sources."

The "integration" can take various forms, such as "providing individual coupling lenses in corresponding lens barrels and integrating the lens barrels with each other" (claim 10), or "integration". The individual coupling lenses may be provided in a common lens barrel and integrated (claim 11), or "the individual coupling lenses may be in close contact with each other" by means such as adhesion (claim 12). ), “A plurality of coupling lenses may be integrally formed” by means such as a mold (claim 13).

Of course, in the coupling optical system according to the ninth to thirteenth aspects, a “collimating lens” may be configured as a coupling lens (claim 14).

According to a fifteenth aspect of the present invention, a light beam from a plurality of light sources is individually coupled by a coupling lens provided for each light source, and each light beam is sub-scanned by a common cylinder lens. Focused in the corresponding direction, imaged as a long linear image in the main scanning corresponding direction near the deflecting reflection surface of the common optical deflector, and deflected light beams deflected by the optical deflector by the common scanning imaging optical system. A multi-beam scanning optical system that converges as a light spot on a surface to be scanned and scans a plurality of scanning lines at a time, includes a coupling lens group and a beam combiner.

In the multi-beam scanning optical system according to the fifteenth aspect, the coupling lenses provided for each light source and constituting the "coupling lens group" have their optical axes in the same plane and are adjacent to each other. The collimating lenses are arranged in the main-scanning corresponding direction such that the optical axes of the collimating lenses form a predetermined angle and the optical axes approach each other on the side of the cylinder lens.

The "combiner" is an "optical element common to each light beam" provided between the coupling lens group and the deflecting / reflecting surface of the optical deflector, and has a negative power at least in the main scanning direction. Have. And the above "each light source"
The light flux coupled by the corresponding coupling lens enters the beam combiner while narrowing the interval in the main scanning corresponding direction, and enters the beam combiner or the cylinder lens while increasing the interval in the sub-scanning corresponding direction. The positional relationship with the optical axis of the corresponding coupling lens is adjusted so that the light is incident.

Like the multi-beam scanning optical system according to the first aspect, also in the multi-beam scanning optical system according to the fifteenth aspect, the lens action of each coupling lens constituting the coupling lens group is determined by a corresponding light source ( (A collimating action) for converting a light beam from a semiconductor laser or an LED into a collimated light beam (claim 22), or a light beam from a corresponding light source to a "weakly converging light beam" or "weakly diverging light beam". Of light. As a common “optical deflector”, a known polygon mirror, rotating two-sided mirror, rotating single-sided mirror, or the like can be used.

In the multi-beam scanning optical system according to the fifteenth aspect, each light beam passing through the beam combiner and the cylinder lens crosses each other at a position near the deflecting reflection surface of the optical deflector in the main scanning corresponding direction. The arrangement can be determined (claim 16). In this way, each light beam is deflected and then separated in the main scanning corresponding direction, and passes through substantially the same optical path in the main scanning corresponding direction with a time difference from each other. It has the same optical characteristics.

In the multi-beam scanning optical system according to the present invention, the scanning and imaging optical system common to each deflection light beam has an fθ lens and a long lens for correcting surface tilt, and a beam combiner and The optical arrangement can be determined so that each light beam passing through the cylinder lens crosses between the fθ lens and the correction long lens in the sub-scanning corresponding direction (claim 17). Similarly to the third aspect of the invention, the operation of the scanning image forming optical system is the same for each deflected light beam in the sub-scanning corresponding direction.

In any of the multi-beam scanning optical systems described in any one of claims 15 to 17, the "beam combiner" may use a mirror (a spherical surface, a cylinder surface, a toroidal surface, etc.) having a negative power. Yes, but a single lens with negative power (a spherical lens, a cylinder lens,
Toroidal lens etc.) "can be suitably used (claim 18). Although both the beam combiner and the cylinder lens are provided between the coupling lens group and the deflecting / reflecting surface, the order may be such that "the beam combiner is provided closer to the coupling lens group side than the cylinder lens". Alternatively, the cylinder lens may be located closer to the coupling lens group than the beam combiner. The beam combiner (Claim 18) and the cylinder lens configured as a single lens having negative power can be combined with each other and integrated (Claim 20). In the multi-beam scanning optical system according to any one of claims 15 to 20, the number of light sources and the number of coupling lenses may be three or more, but may be two (claim 21).

The coupling optical system used as a coupling lens group in the multi-beam scanning optical system according to any one of the fifteenth to twenty-first aspects of the present invention may be configured as follows. Corresponding to
The optical axes are arranged at a predetermined angle with respect to each other and are integrally arranged in a line. "
3). In this case, “the individual coupling lenses are provided in the corresponding lens barrels and the lens barrels are integrated with each other” (claim 24), or “the individual coupling lenses are provided in the common lens barrel”. (Claim 25). In the coupling optical system for a multi-beam scanning optical system according to claim 23 or 25, "a plurality of coupling lenses can be formed integrally with each other" (claim 2).
6). In these cases, “the number of coupling lenses is three” (claim 27), and each coupling lens can be a “collimating lens” (claim 28).

[0028] In the coupling optical system for a multi-beam scanning optical system according to any one of claims 23 to 28, "a surface orthogonal to a plane sharing the optical axis of each coupling lens, The attachment reference portion can be formed in accordance with "a plane which is a plane of symmetry of the ring lens arrangement" (claim 29).

[0029]

FIG. 1 illustrates an embodiment of the invention according to claims 1, 2, 3, 4 and 5 in the case where the number of light sources is two (claim 7). FIG. FIG.
(A) shows a state in which the optical path from the light source section to the surface to be scanned is linearly developed, and the optical arrangement in this state is viewed from the sub-scanning corresponding direction, and the vertical direction is the “main scanning corresponding direction”. . FIG. 3B shows the optical arrangement viewed from the main scanning direction, and the vertical direction is the “sub-scanning direction”.

The light sources 1 and 1 'are "semiconductor lasers", and their light emitting portions are shown in the figure. Symbols 2 and 2 ′ are “coupling lenses” corresponding to the light sources 1 and 1 ′, respectively.
Reference numeral 4 indicates a “beam combiner”, and reference numeral 5 indicates a “cylinder lens”. The beam combiner 4 is a single lens having negative power (Claim 4), and is disposed closer to the light source than the cylinder lens 5 (Claim 5). The cylinder lens 5 has positive power only in the sub-scanning corresponding direction.

A polygon mirror is assumed as the "optical deflector", and its deflecting and reflecting surface is indicated by reference numeral 6 in FIG. Code 7
Is "fθ lens (as described above, the light beam coupled by the coupling lens is a parallel light beam or a light beam having a weak divergence or a weak convergence, and when the coupled light beam is not a parallel light beam, Is not an fθ lens, but is referred to as an fθ lens as described above)),
Reference numeral 8 indicates “a long lens for correcting surface tilt (a long cylinder lens, a long toroidal lens, etc.)”. Lens 7 and a long lens for correcting surface tilt and 8 constitute a "scanning optical system". Reference numeral 9 denotes a surface to be scanned. The surface of the photoconductive photoconductor is provided at the position of the surface to be scanned 9.

The symbol ax is a linear extension of the optical axis of the beam combiner 4 toward the light source and the surface to be scanned, and is hereinafter referred to as a “reference optical axis” for convenience.

As shown in FIGS. 1A and 1B, light beams from a plurality of light sources 1, 1 'are individually coupled by coupling lenses 2, 2' provided for each light beam. A "parallel light beam", a "weak convergence light beam", or a "weak divergence light beam", which is converged in the sub-scanning corresponding direction by a common cylinder lens 5 for each light beam, and is deflected by a common light deflector. Is formed as a line image long in the main scanning corresponding direction in the vicinity of. Each deflected light beam deflected by the optical deflector is condensed as a light spot on the surface 9 to be scanned by the common scanning and imaging optical systems 7 and 8, and scans two scanning lines at a time.

The coupling lenses 2, 2 'provided for each light source are arranged in the main scanning direction with their optical axes parallel to each other to form a "coupling lens group". The optical axes of the coupling lenses 2, 2 'are parallel to the reference optical axis ax, and the coupling lenses 2, 2' are connected to the reference optical axis ax.
Are arranged symmetrically in the main scanning corresponding direction with the symmetry axis as the axis of symmetry.

In each of the light sources 1 and 1 ', the light fluxes coupled by the corresponding coupling lenses 2 and 2' are incident on the beam combiner 4 while "spacing is narrowed in the main scanning corresponding direction" (FIG. 1 ( a)), the positional relationship with the optical axis of the corresponding coupling lens is adjusted so that the light is incident on the beam combiner 4 while increasing the distance in the sub-scanning corresponding direction (FIG. 1B). .

That is, when the principal ray of the light beam radiated from the light sources 1 and 1 'is traced, the following is obtained. Light source 1 is shown in FIG.
As shown in FIG. 2A, the light beam from the light source 1 is disposed slightly away from the optical axis of the coupling lens 2 in the main-scanning corresponding direction to the upper side in the figure.
The principal ray passes through the image-side focal position 3 of the coupling lens 2 and goes obliquely downward in FIG. On the contrary, since the light source 1 'is arranged slightly away from the optical axis of the coupling lens 2' in the main scanning direction in FIG. 1A, the light beam from the light source 1 'is coupled to the coupling lens 2'. Is coupled, the principal ray passes through the image-side focal position 3 'of the coupling lens 2' and goes obliquely upward in FIG. 1A. Therefore, the two light beams coupled by the coupling lenses 2 and 2 ′ enter the beam combiner 4 while “spacing each other” in the main scanning corresponding direction.

The two light beams transmitted through the beam combiner 4 are:
By the operation of the beam combiner 4, the crossing angle in the main scanning corresponding direction is made smaller than before the light enters the beam combiner 4. Thereby, two light beams (in the main scanning corresponding direction)
The crossing position is extended toward the deflecting / reflecting surface 6 so that both light beams cross in the vicinity of the deflecting / reflecting surface 6 in the main scanning corresponding direction. In other words, the positions of the light sources 1 and 1 ', the position of the beam combiner 4, and the position of the cylinder lens 5 are determined so that the two light beams intersect in the main scanning corresponding direction in the vicinity of the deflecting reflection surface 6. 2).

The two light beams reflected by the deflecting / reflecting surface 6 are:
As the deflecting reflection surface 6 rotates, it becomes a deflected light beam, and is condensed as a light spot on the surface 9 to be scanned 9 by the action of the fθ lens 7 and the long lens 8 for correcting surface tilt. At this time, since the two light beams intersect in the vicinity of the deflecting / reflecting surface 6, the light spots formed by the respective light beams are shifted on the surface 9 to be scanned by an interval: Pm in the main scanning direction. Interval: Pm
Are the "imaging magnification" of the scanning imaging optical system, the "negative power" of the beam combiner 4, and the "deviation in the main scanning corresponding direction from the optical axes of the coupling lenses 2 and 2 'of the light sources 1 and 1'. Amount ”,“ focal length ”of coupling lens 2, 22 '
Although it is determined by the above, fine adjustment can be made by adjusting the above-mentioned shift amount.

As described above, by shifting the two light spots on the surface to be scanned by an appropriate interval: Pm in the main scanning direction, two deflection light beams toward the scanning area are separately detected, and each light beam is detected. The start of scanning can be synchronized independently.

Since the light beams from the light sources 1 and 1 'intersect in the vicinity of the deflecting / reflecting surface 6, the two deflecting light beams pass through substantially the same optical path in the main scanning corresponding direction with a time difference. The optical characteristics are the same, and the constant velocity characteristic (fθ characteristic), the field curvature characteristic, and the scanning line bending characteristic of the fθ lens 7 can be made similar for each light beam.

In FIG. 1A, if the beam combiner 4 is not used, the following problems occur. That is,
The distance between the optical axes of the coupling lenses 2 and 2 'is 3 to 15 mm.
Is appropriate from a practical point of view, but when such a large distance between the optical axes, the optical path length from the light source to the deflecting / reflecting surface 6 is to be made comparable to that of the conventional one-beam scanning optical system. Since the “crossing angle in the main scanning corresponding direction” of the light beam from each light source cannot be reduced,
The distance Pm between two light spots in the main scanning direction becomes too large, so that two scanning lines cannot be simultaneously scanned.

Next, as shown in FIG. 1 (b), when viewed from the main scanning corresponding direction, the light sources 1 and 1 'respectively correspond to the corresponding coupling lenses in the sub-scanning corresponding direction (vertical direction in the figure). The light beams from the light sources 1 and 1 'are deviated from the optical axes of the light beams 2 and 2' and are coupled by the corresponding coupling lenses 2 and 2 '. The light intersects at the image-side focal positions 3 and 3 'of the coupling lenses 2 and 2', and thereafter enters the beam combiner 4 while "spreading apart".

When transmitted through the beam combiner 4, the two light beams travel with the positive power of the cylinder lens 5 while gradually narrowing the interval between the two light beams. Form an image. Due to the positive power of the fθ lens 7, the two deflecting light beams by the deflecting reflection surface 6 intersect in the sub-scanning corresponding direction at a position 10 between the fθ lens 7 and the long lens 8 for correcting surface tilt.
(Claim 3) The light is condensed as a light spot on the scanned surface 9 via the long lens 8 for correcting surface tilt. The distance between two light spots in the sub-scanning direction: Ps is the distance between adjacent scanning lines
(Scanning line pitch) or an integral multiple thereof. That is, the distance Ps can be realized by optimizing the focal lengths of the coupling lenses 2, 2 ', the beam combiner 4, the cylinder lens 5, the fθ lens 7, and the long lens 8, and the positions of the light sources 1, 1'.

In the sub-scanning direction, the two deflected light beams intersect at a position 10 between the fθ lens 7 and the long lens 8 for correcting surface tilt. The operation is the same for each deflected light beam, and good correction of surface tilt can be performed for each light beam.

Assuming that the coupling action of the coupling lenses 2, 2 'is a "collimating action" and that a parallel light beam is emitted from the coupling lenses 2, 2', the focal length of the coupling lenses 2, 2 'is adjusted. “Fa”, the focal length of the cylinder lens 5 “Fbs”, the focal length of the beam combiner “Fc”, the focal length of the fθ lens 7 “Fd”, and the intersection of the beam combiner 4 and the two light beams in the main scanning corresponding direction. The distance between the beam combiner 4 and the crossing position of the two light beams in the sub-scanning corresponding direction is "Sbs'", the distance between the fθ lens 7 and the deflecting / reflecting surface is "Sdm", and the cylinder lens 5
Is the distance between the fθ lens 7 and the scanned surface 9 is “Bd”, the distance between the fθ lens 7 and the scanned surface 9 is “Sd”, the fθ lens 7 and the long lens 8 are “Sbs”. The distance between the beam combiner 4 and the cylinder lens 5
Is zero, the shift amount Sm of the light source 1 from the optical axis of the coupling lens 2 in the main scanning corresponding direction is:
Using these and the distance between the light spots: Pm and Ps, Sm = Faa (Pm / (1 + Scm / Fc) / (Bd-SdmSFd) / (Sdm + Fd) / Scm) ( 1), and the shift amount of the light source 1 ′ is obtained by making this value negative. Further, the shift amount Ss of the light source 1 from the optical axis of the coupling lens 2 in the sub-scanning corresponding direction is as follows: Ss = Fa · Ps · (1 / Sbs + Fbs / Fc / (Sbs + Fbs)) · Sds ′ / (Bd-Sds ') (2) where the shift amount of the light source 1' is obtained by making this value negative. The optical axis interval Lm between the coupling lenses 2 and 2 ′ is given by Lm = Sm · (1+ (Scm−Sbs) / Fa (3)

In the above description, the case where the number of light sources and coupling lenses is two has been described (claim 7). The above description is generalized when the number of light sources and coupling lenses is three or more. Is easy. When the number of light sources / coupling lenses is an even number of 3 or more, the same number of coupling lenses as the light sources are provided symmetrically in the main scanning corresponding direction with the reference optical axis ax in FIG. Then, the corresponding light source may be shifted with respect to the optical axis of each coupling lens, and when the number of light sources / coupling lenses is an odd number of 3 or more, the same number of coupling lenses as the light sources are used. What is necessary is just to arrange | position so that the optical axis of the thing in the middle may correspond with reference optical axis ax, and to arrange | position each light source corresponding to each coupling lens. In this case, the light source corresponding to the middle coupling lens has its light-emitting portion arranged “on the optical axis of this coupling lens”.

In the embodiment described with reference to FIG. 1, the order of the beam combiner 4 and the cylinder lens 5 is changed.
The cylinder lens 5 may be provided on the light source side, or the beam combiner and the cylinder lens may be integrated (claim 6). The “integration” may be performed by a method using a mechanical fixing jig, by a method such as bonding, or by integrally forming the beam combiner and the cylinder lens by molding.

FIGS. 2 to 5 show an embodiment of the present invention according to claims 9 to 14 in the case where two coupling lenses are used. In FIG. 2, coupling lenses 2 and 2 'optically equivalent to each other are provided on corresponding lens barrels 2a and 2a' with their optical axes parallel to each other. (Claim 10).

In FIG. 3, the coupling lenses 2 and
2 ′ is provided in a common lens barrel 21 that integrates them (claim 11). In FIG. 4, the common lens barrel 2
The coupling lenses 2 and 2 'provided in the second lens unit 2 are "closely contacted with each other" and integrated (claim 12). FIG.
In the embodiment shown in FIGS. 5A and 5B, two coupling lenses 2 and 2 ′ (FIG. 5A) or two coupling lenses 2b and 2b ′ (FIG. 5B) are integrated. It is formed (claim 13).

FIG. 6 shows a case where the number of light sources is two (claim 21).
9 is a diagram for describing an embodiment of the invention described in 9. FIG.
In order to avoid complication, the same symbols as those in FIG.

FIG. 6A is similar to FIG.
6B is drawn in accordance with FIG. 1B. In FIG. 6A, the vertical direction is the “main scanning corresponding direction”, and in FIG. 6B, the vertical direction is the “sub-scanning corresponding direction”. .

The light sources 1 and 1 'are "semiconductor lasers", and their light emitting portions are shown in the figure. Symbols 2A and 2A 'are "coupling lenses" corresponding to the light sources 1 and 1', respectively.
Is shown. As in FIG. 1, reference numeral 4 denotes a “beam combiner” and reference numeral 5 denotes a “cylinder lens”. The beam combiner 4 is a “single lens having a negative power” (Claim 18), and is disposed closer to the light source than the cylinder lens 5 (Claim 19). The cylinder lens 5 has a positive power only in the sub-scanning corresponding direction. Have.

As in FIG. 1, a polygon mirror (the deflecting / reflecting surface is indicated by reference numeral 6) is assumed as the "optical deflector", reference numeral 7 denotes an "fθ lens", and reference numeral 8 denotes a "length for surface tilt correction". "Length lens", reference numeral 9 indicates a surface to be scanned. The surface of the photoconductive photoconductor is provided at the position of the surface to be scanned 9.
lens 7 and a long lens for correcting surface tilt and 8 constitute a "scanning optical system".

The symbol ax linearly extends the optical axis of the beam combiner 4 to the light source side and the surface to be scanned, and is referred to as the “reference optical axis” as described above.

As in the embodiment shown in FIGS. 1A and 1B, in the embodiment shown in FIGS. 6A and 6B, the light beams from the plurality of light sources 1 and 1 'are , Are individually coupled by coupling lenses 2A and 2A 'provided for each light beam to become a "parallel light beam", a "weakly convergent light beam" or a "weakly divergent light beam". The light is converged in the sub-scanning corresponding direction by the cylinder lens 5 and is formed as a line image long in the main scanning corresponding direction near the deflection reflecting surface 6 of the common optical deflector. Each deflected light beam deflected by the optical deflector is condensed as a light spot on the surface 9 to be scanned by the common scanning and imaging optical systems 7 and 8, and scans two scanning lines at a time.

The coupling lenses 2A and 2A 'provided for each light source have their optical axes on the same plane (reference optical axis a).
The collimating lens 2 is located in a plane including x and the main scanning corresponding direction, that is, in the plane of FIG.
The “coupling lens group” is arranged in such a manner that the optical axes of A and 2A ′ form a predetermined angle: θ, and these optical axes approach each other on the side of the cylinder lens 5 in the main scanning corresponding direction. doing. Coupling lens 2A, 2A '
Is "symmetric with respect to the reference optical axis ax" in the plane.

As shown in FIG. 6 (a), each light source 1, 1 'has a surface including the optical axis of the corresponding coupling lens 2A, 2A' (including the above-mentioned optical axis). Among the planes, the principal ray of the light beam from each of the light sources 1 and 1 'is seen in FIG. 6A with respect to the main scanning corresponding direction. As if they coincided with the optical axes of the corresponding coupling lenses 2A and 2A ', and the coupled luminous fluxes were "closed to each other in the main scanning corresponding direction" while the beam combiner 4
Incident on.

As shown in FIG. 6B, the light sources 1 and 1 'are coupled in the sub-scanning corresponding direction (vertical direction in FIG. 6) with respect to the reference optical axis ax as shown in FIG. The optical axes of the lenses 2A and 2A 'are oppositely and symmetrically shifted from each other. Therefore, the luminous flux from the light sources 1, 1 'is
When coupled by the corresponding coupling lenses 2A and 2A ', the principal rays of each light beam cross at the image-side focal positions 3A and 3A' of the coupling lenses 2A and 2A 'in the sub-scanning corresponding direction, and thereafter. "Spread the gap between each other"
While entering the beam combiner 4. That is, the light source 1,
Reference numeral 1 ′ denotes an optical axis of the corresponding coupling lens so that the light fluxes coupled by the coupling lenses 2A and 2A ′ enter the beam combiner 4 while “spreading each other in the sub-scanning corresponding direction”. The positional relationship has been adjusted.

The two light beams transmitted through the beam combiner 4 are:
By the operation of the beam combiner 4, the crossing angle in the main scanning corresponding direction is made smaller than before the light enters the beam combiner 4. Thereby, two light beams (in the main scanning corresponding direction)
The crossing position is extended toward the deflecting / reflecting surface 6 so that both light beams cross in the vicinity of the deflecting / reflecting surface 6 in the main scanning corresponding direction. That is, in other words, the positions of the light sources 1 and 1 ', the angle between the optical axes of the coupling lenses 2A and 2A': θ, the positions of the beam combiner 4 and the cylinder lens 5 are determined by the two light beams in the main scanning corresponding direction. Are set to intersect in the vicinity of the deflecting reflection surface 6 (claim 16).

The two light beams reflected by the deflecting / reflecting surface 6 are:
As the deflecting reflection surface 6 rotates, it becomes a deflected light beam, and is condensed as a light spot on the surface 9 to be scanned 9 by the action of the fθ lens 7 and the long lens 8 for correcting surface tilt. At this time, since the two light beams intersect in the vicinity of the deflecting / reflecting surface 6, the light spots formed by the respective light beams are shifted on the surface 9 to be scanned by an interval: Pm in the main scanning direction. Interval: Pm
Are the "imaging magnification" of the scanning imaging optical system, the "negative power" of the beam combiner 4, the coupling lenses 2A and 2A.
A ′ “Angle between optical axes: θ”, coupling lens 2,
It is determined by the “focal length” of 22 ′ and the like. The above interval: Pm
When it is necessary to fine-tune the coupling lenses 2A and 2A 'in the main scanning direction,
And the "shift amount" may be adjusted.

As described above, by shifting the two light spots on the surface to be scanned in the main scanning direction by an appropriate distance: Pm, the two deflected light beams traveling toward the scanning area are separately detected, and each light beam is independently detected. As a result, the two deflection light beams pass through substantially the same optical path in the main scanning corresponding direction with a time difference, so that each light beam has the same optical characteristics, and the uniformity characteristic of the fθ lens 7 is obtained. The curvature of field and the curvature of the scanning line can be made similar for each light beam.

In FIG. 6A, if the beam combiner 4 is not used, as in the embodiment of FIG. 1, the distance Pm in the main scanning direction between two light spots on the surface to be scanned becomes large. It is impossible to scan two scanning lines simultaneously.

As shown in FIG. 6B, when the light beams from the light sources 1 and 1 'are coupled by the corresponding coupling lenses 2A and 2A', the principal ray of each light beam is changed in the sub-scanning corresponding direction. Intersect at the image-side focal positions 3A and 3A 'of the coupling lenses 2A and 2A' and thereafter enter the beam combiner 4 while "expanding the distance therebetween" and pass through the beam combiner 4, the two light beams are converted into the cylinder lens 5 Due to the positive power, the light beams travel while gradually narrowing the distance between each other, and each light beam forms a line image long in the main scanning corresponding direction at a position near the deflecting reflection surface 6. The two deflecting light beams by the deflecting reflection surface 6 are converted into the fθ lens 7
At the position 10 between the lens and the long lens 8 for correcting surface tilt, it intersects in the sub-scanning corresponding direction (Claim 17), and the light on the surface 9 to be scanned 9 passes through the long lens 8 for correcting surface tilt. Focus as a spot. The interval Ps between the two light spots in the sub-scanning direction is set to the interval between adjacent scanning lines (scanning line pitch) or an integral multiple thereof. That is, the focal length of the coupling lenses 2A and 2A ', the beam combiner 4, the cylinder lens 5, the fθ lens 7, and the long lens 8 and the position of the light sources 1 and 1' can be optimized to realize the above-mentioned interval: Ps.

As in the embodiment shown in FIG. 1, the two deflecting light beams intersect at the position 10 between the fθ lens 7 and the long lens 8 for correcting surface tilt in the sub-scanning corresponding direction. The effect of the long lens 8 for correction is the same for each deflected light beam, and good correction of surface tilt can be performed for each light beam.

In the case of the embodiment shown in FIG.
The shift amount Ss of the light source 1 in the sub-scanning corresponding direction from the optical axis of the coupling lens 2A is given by the above equation (2). The shift amount of the light source 1 ′ is “a value obtained by making the value of Expression (2) negative”.

The angle θ formed by the optical axes of the coupling lenses 2A and 2A 'is determined as follows.

That is, the focal length of the coupling lenses 2A and 2A ': Fa, and the focal length of the cylinder lens 5: Fb
s, focal length of the beam combiner: Fc, focal length of the fθ lens 7: Fd, interval between the beam combiner 4 and the crossing position of the two light beams in the main scanning direction: Scm, beam combiner 4
And the distance between the two light beams in the sub-scanning corresponding direction: Sbs',
The distance between the fθ lens 7 and the deflecting / reflecting surface: Sdm, the image-side focal point 3 of the cylinder lens 5 and the coupling lens 2, 2 ′,
3 ′: Sbs, distance between fθ lens 7 and scanned surface 9: Bd, distance between fθ lens 7 and long lens 8: Sd
Assuming that s ′ is the same as that of the embodiment of FIG. 1 and that the distance between the beam combiner 4 and the cylinder lens 5 is 0, FIG.
In order to make the Pm in the embodiment of the present invention equal to the Pm in the embodiment of FIG. 1, the light source 1 in the embodiment of FIG. 1 corresponds to the main scanning from the optical axis of the coupling lens 2. The relationship: θ = 2tan ~ ¹ (Sm / Fa) (4) may be established between the deviation amount in the direction: Sm and the angle: θ. Therefore, in the embodiment of FIG. 1, if the above-mentioned deviation amount: Sm is determined, it is used to calculate the angle:
By calculating θ, the embodiment of FIG. 6 can be implemented with optical characteristics equivalent to those of the embodiment of FIG.

Although the above description has been made of the case where the number of light sources and coupling lenses is two (claim 21), the above description is generalized when the number of light sources and coupling lenses is three or more. Is easy. When the number of light sources / coupling lenses is an even number of 3 or more, the same number of coupling lenses as the light sources are provided symmetrically in the main scanning corresponding direction with the reference optical axis ax in FIG. Then, the corresponding light source may be displaced in the sub-scanning corresponding direction with respect to the optical axis of each coupling lens. If the number of light sources / coupling lenses is an odd number of 3 or more, the same number of light sources as The coupling lens may be provided so that the optical axis of the middle one coincides with the reference optical axis ax, and each light source may be provided corresponding to each coupling lens. In this case, the light source corresponding to the middle coupling lens has its light-emitting portion arranged “on the optical axis of this coupling lens”.

In the embodiment described with reference to FIG. 6 as well, the order of the beam combiner 4 and the cylinder lens 5 may be reversed, the cylinder lens 5 may be provided on the light source side, or the beam combiner and the cylinder lens may be integrated. Good (claim 20). The “integration” may be a method using a mechanical fixing jig, a method such as bonding, or the beam combiner and the cylinder lens may be integrally formed from the beginning by molding.

FIGS. 7 to 9 show an embodiment of the invention according to claims 23 to 29. That is, FIGS.
In the embodiment shown in FIG. 1, a “coupling optical system” used as a coupling lens group is a coupling lens that is optically equivalent to each other, and has optical axes that form a predetermined angle with respect to each of the light sources. In this way, they are arranged and integrated in a row.

In the coupling optical system 25 shown in FIG.
Three coupling lenses 2B optically equivalent to each other,
In 2B ′ and 2B ″, the optical axes of the adjacent coupling lenses are arranged and integrated in a series so that the optical axis forms an angle θ ₁ with each other (claims 26 and 27).

In the coupling optical system 30 shown in FIG.
Two coupling lenses 2A optically equivalent to each other,
2A 'such that the optical axes make a predetermined angle with each other,
The lens barrels 2a and 2a 'are provided in the corresponding lens barrels 2a and 2a'.
a and 2a 'are integrated with each other (claim 24).
Furthermore, a surface orthogonal to a plane sharing the optical axis of each of the coupling lenses 2A and 2A ', which is a symmetrical surface of the coupling lens arrangement, that is, the coupling optical system 30 is moved from the direction corresponding to the sub-scanning direction. The mounting reference portion a is aligned with the plane including the straight line A in FIG.
Are formed as protrusions (claim 29). An engagement portion that engages with the attachment reference portion a is formed in a portion where the coupling optical system 30 can be attached, and attachment is performed such that the longitudinal direction of the attachment reference portion a is parallel to the reference optical axis ax. Thus, the coupling optical system can be easily and reliably mounted in an appropriate position.

In the coupling optical system 40 shown in FIG.
The three coupling lenses 2B, 2B ', 2B''
The optical axes are arranged in a line so as to form a predetermined angle with each other and are provided in the common lens barrel 2b.
5). Furthermore, each coupling lens 2B, 2
A plane orthogonal to a plane sharing the optical axis of B ′, 2B ″ and a plane that is a symmetry plane of the coupling lens array (FIG. 9)
In this case, the mounting reference portion a ′ is formed in a projection shape so as to match the plane including the straight line A and perpendicular to the drawing, and mounting is performed using the individual mounting reference portions a ′.
The coupling optical system can be easily and reliably mounted in an appropriate position.

Of course, the coupling lens of the coupling optical system shown in FIGS. 7 to 9 can be used as a collimator lens.

[0075]

EXAMPLES Specific examples will be described below. Each embodiment has an optical arrangement in which the order of the cylinder lens 5 and the beam combiner 4 in the embodiment described with reference to FIG. The action of the coupling lens is a collimating action, and the coupled light flux becomes a parallel light flux.

The focal length of the cylinder lens 5 is 100 m
m, the focal length of the beam combiner 4 is -50 mm, fθ
The focal length of the lens 7 is 200 mm, and the fθ lens 5
Is from −50 mm to the deflection reflecting surface 6 of the optical deflector (polygon mirror), and 70 mm from the long lens 8 to the scanning surface 9.

The “cylinder lens position” refers to the coupling lens 2, 2 ′ with respect to the cylinder lens 5.
The distance between the optical axes of the coupling lenses 2 and 2 ′ arranged in the main scanning direction is referred to as “light source shift amount (main)”. There is a shift amount in the main scanning corresponding direction between the light source and the optical axis of the corresponding coupling lens, and a “light source shift amount (secondary)” is a shift amount between the light source and the optical axis of the corresponding coupling lens. This shows the amount of deviation in the scanning corresponding direction. This “shift amount” is symmetrical with respect to the two light sources, and the signs are only opposite to each other. Therefore, only one light source is shown.

The “beam combiner position” indicates the distance (positive) from the beam combiner 4 to the deflecting / reflecting surface 6.
“Image plane pitch (main) and (sub)” indicates the distance (Pm, Ps described above) between two light spots formed on the surface to be scanned in the main scanning direction and the sub-scanning direction.

In the first to fourth embodiments, the focal length of the coupling lens (collimating lens) is 8 mm.

Example No. 1 2 3 4 Cylinder lens position -125 -125 -125 -125 Optical axis interval 3.78 5.23 4.63 6.41 Light source shift amount (main) 0.198 0.242 0.242 0.296 Light source shift amount (secondary) 0.040 0.040 0.040 0.040 Beam combiner Position 33.33 200.00 33.33 200.00 Image plane pitch (main) 2 2 3 3 Image plane pitch (secondary) 0.0635. 0.0635 0.0635 0.0635.

In the following Examples 5 to 8, the focal length of the coupling lens (collimating lens) is 16 mm.
It is.

Example No. 5 6 7 8 Cylinder lens position -125 -125 -125 -125 Optical axis interval 3.98 5.47 4.87 6.70 Light source shift amount (main) 0.395 0.484 0.484 0.593 Light source shift amount (secondary) 0.079 0.079 0.080 0.080 Beam combiner Position 33.33 200.00 33.33 200.00 Image plane pitch (main) 2 2 3 3 Image plane pitch (secondary) 0.0635. 0.0635 0.0635 0.0635.

In the first to eighth embodiments, the scanning density is 400 d
pi.

In the following embodiments 9 to 12, the focal length of the coupling lens (collimating lens) is 8 mm.
It is.

Example No. 9 10 11 12 Cylinder lens position -150 -150 -150 -150 Optical axis interval 4.40 5.99 5.38 7.33 Light source shift amount (main) 0.198 0.242 0.242 0.296 Light source shift amount (secondary) 0.012 0.012 0.012 0.012 Beam combiner Position 33.33 200.00 33.33 200.00 Image plane pitch (main) 2 2 3 3 Image plane pitch (secondary) 0.0423. 0.0423 0.0423 0.0423.

In Examples 13 to 16 mentioned last, the focal length of the coupling lens (collimating lens) is 16
mm.

Example No. 13 14 15 16 Cylinder lens position -150 -150 -150 -150 Optical axis interval 4.59 6.23 5.63 7.63 Light source shift amount (main) 0.395 0.484 0.484 0.593 Light source shift amount (secondary) 0.024 0.024 0.024 0.024 Beam combiner Position 33.33 200.00 33.33 200.00 Image plane pitch (main) 2 2 3 3 Image plane pitch (secondary) 0.0423. 0.0423 0.0423 0.0423.

In Embodiments 9 to 16, the scanning density is 600
dpi.

The image plane pitch (main), which is the distance between the two light spots in the main scanning direction, is 2 m, as described above, as a value that can independently and accurately synchronize each light beam.
m and 3 mm. The optical axis interval covers from about 4 mm at which the two coupling lenses are in close contact (in the case of FIG. 4) to about 8 mm in which the lens barrel holding each coupling lens is in close contact (in the case of FIG. 3). In these embodiments 1 to 16, the light source shift amount is (main)
Both values are reasonable and not too large or too small to make adjustment difficult.

In the above description, the combination of the fθ lens and the long lens has been described as the scanning image forming optical system.
Alternatively, the scanning imaging optical system can be configured as an optical system including a concave mirror. In the embodiment shown in FIG. 1, one or more optical path bending mirrors for bending the optical path according to the layout of the scanning optical system may be appropriately arranged on the optical path from the light source to the surface to be scanned. Needless to say.

In Embodiments 1 to 16 described above, the two coupling lenses constituting the coupling lens group are:
Although the optical axes are parallel to each other, as in the embodiment shown in FIG. 6, the optical axes of the two coupling lenses may form a predetermined angle θ with each other. Thus, 2
In the case where the optical axes of the coupling lenses are made non-parallel, the “light source shift amount (Eq. 4)”, that is, “θ = 2 tan S ¹ (Sm / Fa)” in the above Examples 1 to 16 is used. Main) ”into the angle: θ.

That is, “Sm” in equation (4) is “light source shift amount (main)” in each of the above embodiments, and “Fa” is
Since it is the focal length of the coupling lens, the quotient of these values is obtained, and the arc tangent is doubled to obtain the angle θ.

For example, in the case of the first embodiment, since Sm = 0.198 mm and Fa = 8 mm, (Sm /
Fa) = 0.198 / 8 = 0.02475, and tan ~ ¹ (Sm / F
a) = 1.42 degrees. From this, the optical axes of the coupling lenses in the first embodiment cross each other at an angle of 2.84 degrees, and the shift amount of the light source in the main scanning direction, that is, the light source shift amount
If (main) is set to 0, the embodiment of FIG. 6 can realize the same state as that of the first embodiment. Also in Embodiments 2 to 16, the “light source shift amount (main)” can be converted into the crossing angle of the optical axis of the coupling lens by the same calculation.

[0094]

As described above, according to the present invention, a novel multi-beam scanning optical system can be realized. The multi-beam scanning optical system according to the present invention does not use an expensive polarizing beam splitter to combine a plurality of light beams, so that the cost can be reduced, and three or more light beams can be combined by one beam combiner. It is easy to make multiple beams.

According to the second and 16th aspects of the present invention, the deflection light beam passes through the same position of the scanning image forming optical system for each deflection light beam in the main scanning direction. Since a plurality of light spots are separated by a necessary interval in the main scanning direction, each deflected light beam can be accurately separated and detected, and it is easy to individually synchronize the scanning for each deflected light beam.

According to the third and 17th aspects of the present invention, the surface tilt correction function of the scanning image forming optical system operates in the same manner for each deflected light beam, so that the scanning line pitch hardly fluctuates between image heights.

In the coupling optical system for a multi-beam scanning optical system according to the present invention, since a plurality of coupling lenses are fixed close to each other, the coupling optical system is hardly affected by mechanical vibrations and environmental changes, and scanning line pitch fluctuations and the like. In addition, problems unique to multi-beam scanning hardly occur.

[Brief description of the drawings]

FIG. 1 is a view for explaining one embodiment of a multi-beam scanning optical system according to the first embodiment.

FIG. 2 is a diagram showing an embodiment of a coupling optical system for a multi-beam scanning optical system.

FIG. 3 is a diagram showing another embodiment of the coupling optical system for the multi-beam scanning optical system.

FIG. 4 is a diagram showing another embodiment of the coupling optical system for the multi-beam scanning optical system.

FIG. 5 is a diagram showing another embodiment of the coupling optical system for the multi-beam scanning optical system.

FIG. 6 is a view for explaining an embodiment of the multi-beam scanning optical system according to claim 15;

FIG. 7 is a diagram showing an embodiment of a coupling optical system for a multi-beam scanning optical system.

FIG. 8 is a diagram showing another embodiment of the coupling optical system for the multi-beam scanning optical system.

FIG. 9 is a diagram showing another embodiment of the coupling optical system for the multi-beam scanning optical system.

[Explanation of symbols]

 1, 1 'Light source 2, 2' Coupling lens 4 Beam combiner 5 Cylinder lens 6 Deflective reflecting surface 7, 8 Scanning optical system 9 Scanned surface

Claims (29)

[Claims] A light beam from a plurality of light sources is individually coupled by a coupling lens provided for each light source, and each light beam is converged in a sub-scanning corresponding direction by a common cylinder lens. An image is formed as a long line image in the main scanning direction near the deflection reflecting surface of the deflector, and each deflected light beam deflected by the optical deflector is condensed as a light spot on the surface to be scanned by a common scanning image forming optical system. In a multi-beam scanning optical system that scans a plurality of scanning lines at a time, the coupling lenses provided for each light source are arranged in the main scanning corresponding direction with their optical axes parallel to each other to form a coupling lens group. A beam combiner having a negative power at least in the main scanning corresponding direction is commonly provided between the coupling lens group and the deflection reflecting surface of the optical deflector for each light beam. The light beam coupled by the coupling lens is incident on the beam combiner while narrowing the interval in the main scanning corresponding direction, and is incident on the beam combiner or the cylinder lens while increasing the interval in the sub-scanning corresponding direction. As
A multi-beam scanning optical system, wherein a positional relationship between a corresponding coupling lens and an optical axis is adjusted. 2. The multi-beam scanning optical system according to claim 1, wherein the respective light beams passing through the beam combiner and the cylinder lens cross each other at a position near the deflection reflecting surface of the optical deflector in the main scanning corresponding direction. A multi-beam scanning optical system, wherein an optical arrangement is determined. 3. A multi-beam scanning optical system according to claim 1, wherein the scanning image forming optical system common to each deflected light beam has an fθ lens and a long lens for correcting surface tilt. A multi-beam scanning optical system, wherein an optical arrangement is determined so that each light beam passing through a cylinder lens crosses between the fθ lens and a long lens for correction in a sub-scanning corresponding direction. 4. A multi-beam scanning optical system according to claim 1, wherein said beam combiner is a single lens having a negative power. 5. The multi-beam scanning optical system according to claim 4, wherein the beam combiner is provided on the coupling lens group side with respect to the cylinder lens. 6. The multi-beam scanning optical system according to claim 4, wherein the beam combiner and the cylinder lens are integrated. 7. The multi-beam scanning optical system according to claim 1, wherein the number of light sources and the number of coupling lenses are two. 8. The multi-beam scanning optical system according to claim 1, wherein the coupling action of each coupling lens in the coupling lens group is a collimating action. Optical system. 9. A coupling optical system used as a coupling lens group in the multi-beam scanning optical system according to any one of claims 1 to 7, wherein a coupling lens optically equivalent to each other is provided as a light source. A coupling optical system for a multi-beam scanning optical system, wherein the optical axes are parallel to each other and are arranged and integrated in a single row. 10. A coupling optical system for a multi-beam scanning optical system according to claim 9, wherein each coupling lens is provided in a corresponding barrel.
The lens barrels are integrated with each other,
Coupling optical system for multi-beam scanning optical system. 11. A coupling optical system for a multi-beam scanning optical system according to claim 9, wherein each coupling lens is provided in a common lens barrel. Coupling optics. 12. A coupling optical system for a multi-beam scanning optical system according to claim 9, wherein the individual coupling lenses are in close contact with each other. . 13. The coupling optical system for a multi-beam scanning optical system according to claim 12, wherein a plurality of coupling lenses are formed integrally with each other. Ring optics. 14. A coupling optical system for a multi-beam scanning optical system according to claim 9, wherein each coupling lens is a collimating lens. Coupling optics. 15. A light beam from a plurality of light sources is individually coupled by a coupling lens provided for each light source, and each light beam is converged in a sub-scanning corresponding direction by a common cylinder lens. An image is formed as a long line image in the main scanning direction near the deflection reflecting surface of the deflector, and each deflected light beam deflected by the optical deflector is condensed as a light spot on the surface to be scanned by a common scanning image forming optical system. In a multi-beam scanning optical system that scans a plurality of scanning lines at a time, the coupling lenses provided for each light source have their respective optical axes in the same plane, and the optical axes of the collimating lenses that are adjacent to each other are different from each other. A coupling lens group is arranged in the main scanning corresponding direction so as to form a predetermined angle and such that their optical axes approach each other on the side of the cylinder lens. A beam combiner having a negative power at least in the main scanning corresponding direction is commonly provided for each light flux between the lens group and the deflecting and reflecting surface of the optical deflector, and each light source is coupled by a corresponding coupling lens. The light flux is incident on the beam combiner while narrowing the interval with respect to the main scanning corresponding direction, and is incident on the beam combiner or the cylinder lens while widening the interval with respect to the sub-scanning corresponding direction,
A multi-beam scanning optical system, wherein a positional relationship between a corresponding coupling lens and an optical axis is adjusted. 16. A multi-beam scanning optical system according to claim 15, wherein the light beams passing through the beam combiner and the cylinder lens cross each other at a position near the deflection reflecting surface of the optical deflector in the main scanning corresponding direction. A multi-beam scanning optical system, wherein an optical arrangement is determined. 17. The multi-beam scanning optical system according to claim 15, wherein the scanning and imaging optical system common to each deflection light beam has an fθ lens and a long lens for correcting surface tilt, A multi-beam scanning optical system, wherein an optical arrangement is determined so that each light beam passing through a cylinder lens crosses between the fθ lens and a long lens for correction in a sub-scanning corresponding direction. 18. A multi-beam scanning optical system according to claim 15, wherein the beam combiner is a single lens having a negative power. 19. The multi-beam scanning optical system according to claim 18, wherein the beam combiner is provided closer to the coupling lens group than the cylinder lens. 20. The multi-beam scanning optical system according to claim 18, wherein a beam combiner and a cylinder lens are integrated. 21. The multi-beam scanning optical system according to any one of claims 15 to 20, wherein the number of light sources and the number of coupling lenses are two. 22. The multi-beam scanning optical system according to claim 15, wherein the coupling action of each coupling lens of the coupling lens group is a collimating action. Optical system. 23. A coupling optical system used as a coupling lens group in the multi-beam scanning optical system according to any one of claims 15 to 21, wherein a coupling lens optically equivalent to each other is used as a light source. A coupling optical system for a multi-beam scanning optical system which is arranged and integrated in a single line so that the optical axes make a predetermined angle with each other. 24. A coupling optical system for a multi-beam scanning optical system according to claim 23, wherein each coupling lens is provided in a corresponding lens barrel,
The lens barrels are integrated with each other,
Coupling optical system for multi-beam scanning optical system. 25. A coupling optical system for a multi-beam scanning optical system according to claim 23, wherein each coupling lens is provided in a common lens barrel. Coupling optics. 26. A coupling optical system for a multi-beam scanning optical system according to claim 23, wherein a plurality of coupling lenses are formed integrally with each other. Coupling optics. 27. A coupling optical system for a multi-beam scanning optical system according to any one of claims 23 to 26, wherein the number of coupling lenses is three. Coupling optics for 28. A coupling optical system for a multi-beam scanning optical system according to any one of claims 23 to 27, wherein each coupling lens is a collimating lens. Coupling optics. 29. The coupling optical system for a multi-beam scanning optical system according to any one of claims 23 to 28, wherein the surface is orthogonal to a plane sharing the optical axis of each coupling lens, A coupling optical system for a multi-beam scanning optical system, wherein a mounting reference portion is formed in accordance with a plane which is a symmetric plane of the coupling lens array.